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Same challenges, diverse solutions: Outcomes of a crosslinguistic
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The project thus had an initial practical and clinical motivation. However, other major objectives concerning the project were both theoretical and data-oriented. Over the past century, language researchers have analysed patterns across and within languages in order to determine the degree of similarity/universality of language systems. For the developing human being, this question concerns the relative influence of environment versus innateness in language acquisition. Regarding many aspects of language, typically developing children appear to have a similar maturational timetable across languages (e.g., Berko-Gleason & Bernstein Ratner, 2009; Jakobson, 1941/1968). However, researchers have also noted differences that reflect the language being learned (e.g., Ingram, 2012;
Pye, Ingram, & List, 1987). What appears to be complex and late-acquired in one language may be early-acquired in another, depending on the frequency of the element and its functionality in the language. Crosslinguistic data are crucial for addressing this fundamental question about language, yet very few studies concerning one aspect of language development, phonological development, have been conducted using equivalent methodology across languages. The overarching objective of the crosslinguistic study is therefore to inform linguistic theories further on the questions of universality and diversity in phonological development, through analyses of child speech data from a variety of languages.
For ‘adult’ phonology, researchers have investigated both the structure of words (sequences of consonants and vowels, syllable formation, word stress) and segments (consonants/vowels) and their composite features across a wide range of languages (e.g., de Lacy, 2007). However, a comprehensive crosslinguistic comparison of word structure, segments and their interactions remains to be done for developing phonological systems, specifically taking into account the relative levels of complexity within each language. Within-language analyses in the project have revealed strong interactions between the stress and structure of the syllable and the mismatch patterns observed (e.g., Chávez- Peón et al., 2012), e.g., unstressed syllables showing many more and different mismatch patterns than stressed syllables. However, to address the main question of the proposed study concerning universality, additional within- and between-language comparisons need to be done that can take into account language type and relative complexities. Thus, a second major objective of the proposed study has been to conduct within- and between-language comparisons of segments, word structures and their interactions, both to learn more about various aspects of developing phonological systems and to address the question of universality.
While expecting both similarities and differences in developmental data across languages, diversity in sampling and transcription conventions during the project necessitated considerations of a number of methodological variables in addition to interpretation of differences in results. The following paper provides an overview of the diversity observed in methodology and results, and the solutions and interpretations applied. The major purposes of the current paper are thus to provide an overview of the study and initial results, to suggest strategies that may assist in future crosslinguistic research and to provide a link to resources that may be useful both clinically and for research. The paper begins with general methodology for the project, including solutions to the similar challenges in diversity of sampling and transcription. The subsequent section addresses within-language diversity, focusing on considerations of dialectal influence (Mandarin, Granada Spanish) on children's pronunciations, and the interaction of word structure and features in interpreting variable developmental patterns. The third section outlines similarities and differences in German, English and Icelandic fricative production by children with protracted phonological development, reflecting an influence of inventories and frequency within the languages. Discussion is woven throughout the paper, rather than included in a separate section. The paper explores implications of the current study for future research, and provides links to project resources for clinical and research purposes.
Methodology
The following section outlines the general methodology for the study in terms of data collection and analysis. Subsequent sections outline two of the common ways that methodology diverges across languages: sampling differences and transcription conventions. Finally, the project's solutions to those differences are presented and discussed.
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The objective across languages is to collect data from 20-30 monolingual children aged 3-6 years and designated locally as having protracted phonological development (PPD). Exclusion criteria include sensorineural hearing loss, severe chronic otitis media, major language comprehension or cognitive delays and major orofacial anomalies. Limited sentence production is not an exclusionary criterion. In addition, if local funds permit, data are also collected from typically developing (TD) children matched for age and dialect area to the PPD cohort. A native speaker tests the children in a quiet room, usually in a preschool centre, in a 45-60 minute session. The data are digitally recorded with a high quality audio-recording device (most often with a M-Audio Microtrack II digital recorder and a Sennheiser remote system, i.e. transmitter EK 100 G2 and receiver SK 100 G2, with Countryman remote lapel microphones). If possible, video recordings are also made. For each language, an approximately 100-word list is developed for photo elicitation; project leaders and local investigators choose words familiar to children that cover all segments of the language (both consonants and vowels, at least twice across word positions) and the major word structures (stress patterns, CV sequences). Ten words are elicited three times each using either pictures or objects as a warm-up and to assess within-word variability later. Additional testing includes a hearing screening and a language comprehension test (where available), a short spontaneous language sample, and a one-page parental questionnaire about the child’s development and language use. Following development of a transcription-conventions document in conjunction with the local team and project leaders, a native speaker of the dialect area transcribes the sample, with reliability of transcription confirmed with a second native speaker or project leader experienced with transcription. (Further discussion of transcription follows below.) Data are then entered into Phon, a free phonological program for entry and analysis of phonological development data (http://childes.psy.cmu.edu/phon/), either locally or in the first author's laboratory at the University of British Columbia. Data are double-checked for accuracy of adult targets and alignment. Exportation of the data into spreadsheets allows data analysis in addition to what is provided by the phonological analysis program.
As can be seen above, the objective is to provide a common methodology across languages with similar (1) sample characteristics, (2) word list types, (3) data collection procedures, (4) transcription conventions and (5) data entry and analysis procedures. While the objective is generally achieved for items (2), (3) and (5), items (1) and (4) are more challenging. They are addressed in more detail below.
Sampling characteristics
As with all human-subject research, research is constrained by the availability of participants and by the time and resources available. The recruitment process can be slow for any number of legitimate reasons. In the end, we celebrate the participants that do agree to be part of our project, whether they match the numbers we desire or are at the preferred ages or developmental levels. Many language teams were able to find the target number of participants in the designated age range, including matched control groups of TD children, but not all. Furthermore, there were small variations in the number of children by age, reflecting the recruitment challenges. Relative to degree of PPD, preliminary data analysis showed that degree of PPD might not be equivalent across all languages. A Whole Word Match (WWM) was calculated for the various samples, showing ranges from less than 12% average across the cohort with PPD (English, Icelandic) to about 40% for Mandarin and Granada Spanish. (Whole Word Match means that the child’s pronunciation of a word matches the adult target, or is considered “close enough” by adult native speakers, with slight deviations in place or voicing ignored; Schmitt, Howard, & Schmitt, 1983.) The first question was whether the word lists from different languages were too different to compare, because the Germanic languages are more complex in word structure than Mandarin and Spanish, even for words familiar to children (e.g., more clusters, codas). However, looking at data for TD 4-year-olds, the WWM was 80% for Kuwaiti Arabic (with complex phonology) and Mandarin, and 85% for the Spanish-speaking children, i.e. virtually equivalent. Differences across languages in sampling characteristics for the cohorts with PPD more likely reflect variation in who was designated as having PPD. For the researcher, the question is how to resolve this kind of discrepancy. The discrepancy is not particularly important for within-language
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analyses, except when comparing experimental and control groups. The WWM scores did allow evaluation of the PPD classification, when there were matched groups of control participants included. For example, in the Granada Spanish cohort, one child originally designated as PPD had a WWM similar to the age-matched controls, and thus was reassigned to that cohort. Overall, however, the original classification as TD vs PPD was consistent with the WWM scores. Regarding between- language comparisons, discrepancies within groups are important. Thus, before analysis, matched samples are selected by age, gender (where possible) and various global phonological measures, e.g., WWM or Percent Consonants Correct (PCC) scores. If global phonological variables match, then validity of more specific between-language comparison is enhanced. Participant matching reduces the sample sizes and power, but provides more assurance that interpretation is based on phonological differences rather than sampling differences.
Transcription conventions
As is well-documented, achieving transcription agreement is difficult even for transcribers who speak the same language and have the same amount and type of training. This is particularly true for child speech or more 'disordered' speech, and if the transcribers use narrower transcription (Shriberg & Lof, 1991). Consensus-building activities and practice can enhance reliability, as can acoustic analysis, e.g., examining VOT, frication, formants, nasality, or duration (Bernhardt & Stemberger, 2012). Some of the differences and solutions for broad transcription conventions for reliability have been as follows:
1. Transcribers differ on whether to include or exclude a predictable word-initial glottal stop when not phonemic in the language. The convention of the local transcription team was followed. For analysis, even transcribed word-initial glottal stops were counted as deletions if a target consonant was missing, but identified as glottal stops for future considerations.
2. Standard local transcription preferences are generally followed, but are taken into account for cross-linguistic comparisons. For example, in Spanish, what is transcribed as palatoalveolar t ] (implying retracted tongue tip) is actually alveolopalatal t ] (with advanced tongue tip;
Kochetov & Colantoni, 2011), but is nevertheless transcribed as t ]. In Icelandic, what is transcribed as palatal [c] is actually a fronted velar k ] (Árnason, 2011), but is transcribed as [c]. For Swedish, consonant length in adult speech is predictable from vowel length (Schaeffler & Wretling, 2003), and is therefore not transcribed.
Regarding narrow transcription, a number of differences arose during transcription comparisons and were resolved as follows:
1. For Granada Spanish, a number of conventions apply for allophonic variation. Because lenition of voiced stops (e.g., /b/ as β]) is expected intervocalically, and the fricative/
approximant is not phonemically different from a stop that the child might use instead, the native speaker transcribers did not always note this allophonic difference in the transcript. A non-native transcriber verified stop vs continuant allophones spectrographically, and adjusted the adult target appropriately. That way, the data were maintained for future use, but no mismatch was indicated for the child, in agreement with the initial transcription. Similarly, when coda /s/ deletes in Granada Spanish, a small [h] or short [h]-like element can replace it (Martínez Celdrán & Fernández Planas, 2007). The second transcriber verified presence of aspiration on the spectrogram, and included the [h] in both the adult and child forms, but the difference is not considered clinically relevant. For both Granada Spanish and Icelandic, voiced “fricatives” are generally more approximant-like (Martínez Celdrán & Fernández Planas, 2007; Árnason, 2011). However, they ware transcribed using fricative symbols, in accordance with local transcription conventions.
2. Sometimes children appear to epenthesize a small vocalic element either after a coda consonant or between cluster elements. Native adult speakers may also have short transitional elements in certain clusters that are ignored as irrelevant. Generally, epenthetic “vowels”
shorter than 40 milliseconds are examined acoustically by a second transcriber and written as superscripts (e.g., ˈgᵊris]), with vowels of 60 msec or longer written on the line as vowels
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(e.g., gəˈris]). This arbitrary convention is currently being verified in an ongoing study of clusters.
3. A child's vocal tract anatomy generally includes a high flattish tongue body in a proportionally small (by adult standards) oral cavity. Thus, sibilants such as /s/ are often de- grooved or flattened, and the tongue body is high enough to cause frication along a longer axis than in adult speech. For the study, an attempt was made to distinguish such productions from [s]/[z] by transcribing them as [sθ]/[zð] (if dentalized with a flattish (but not fully flat) tongue and a low-enough tongue body), or alveolopalatal ]/ ʑ] (if ungrooved with a too- high tongue body).
Although full agreement is unlikely across languages, the reliability of transcription has been enhanced by this method. For the Granada Spanish, after consensus-building, agreement for segments was high: 96% for TD samples and 93.6% for PPD samples. What has become clear during the consensus-building process is that most transcribers hear and agree on most aspects of the child’s pronunciation, when brought to their attention. One difference across languages is that different things are considered irrelevant for transcription, because of differing local conventions or assumptions about importance for adult or clinical populations. The team learns together how to agree on what matters, what symbols to use, and how to interpret the symbols. As a final note, the development of transcription conventions includes identification of multiple acceptable adult targets in the dialect area, so that children are not penalized for “nonstandard” pronunciations learned from adult input. We return to such variation in adult speech in the next section.
Within-language results: Diversity and methods of analysis
Above we alluded to one of the key considerations for within-language analysis: what the adult target might be. This has proven to be relatively challenging for all of the languages. Even well-trained native speakers can be unaware of how their idiolect reflects or does not reflect the local dialect vs the standard. For the study, speech samples have been collected from at least one adult from the dialect area, but with too few speakers to adequately reflect adult variation. In addition, the teams have consulted literature on the dialect. Through meetings with the local teams, time is spent in determining what the range of possibilities for the adult targets might be. For Granada Spanish, data were collected from three adults from the same area. Not only did use of [s] (seseo) vs θ] (ceceo) differ across speakers, but also within speakers. Other coda consonants can also be fully present, reduced, or absent. As noted, coda [s] may be replaced by [h] or ʰ], with a laxing of the vowel quality: e.g., dos ‘two’ dos]~ dɔh]~ dɔʰ]. Coda [l] and [r] can interchange, or delete, in the case of the medial consonant, with gemination of the following consonant: e.g., alma 'soul' alma/aɾma/amːa] or sarten 'frying pan' saɾˈten/salˈt /saˈtː ] (note also /n/ deletion with vowel nasalization). The child’s pronunciation may be based on different adult targets, and all variants must be noted in the adult target set.
A more complex example is given below concerning Mandarin (also known as Putonghua). Mandarin is the most widespread language in China. Children start learning Mandarin at preschool around age 3, if they are not already speaking it natively. The phonetic inventory of standard Mandarin is presented in Table 1.
Coronal fricatives and affricates are a major component of the Mandarin consonant inventory, with contrasts in tongue-tip placement and height of the tongue body: dentals (with advanced tongue tip and low tongue body), alveolopalatals (with advanced tongue tip and high tongue body), and retroflexes (with retracted tongue tip). The laryngeal contrast is between voiceless unaspirated vs voiceless aspirated stops and affricates.
Data were collected from a group of 30 TD 4-year-olds in Shanghai, with an average of WWM of 80%. Several of the low frequency mismatch patterns provide insight into the dialect question (see Table 2 for the number of children showing various mismatches).
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Table 1. Standard Mandarin phonetic inventory.
Because Mandarin has a large number of articulatorily complex coronal fricatives and affricates, it is tempting to say that these may just be late-developing. Some children may still be learning the rhotic consonant and vowel, as well as other coronals; there are some dorsal-coronal interchanges, suggesting further that the retroflex issue is developmental. However, Shanghainese (the local language spoken in Shanghai before the introduction of Mandarin) does not have retroflex sibilants, and Shanghainese-influenced Mandarin may lack retroflexes. Some Shanghainese Mandarin speakers, particularly young adult women (potentially the mothers of the children in this centre) (Starr &
Juraksy, 2004) are showing a hyper-correction phenomenon, using retroflexes where they are not in the adult Mandarin target. Some children may be exposed to adult pronunciations with these nonstandard sibilant productions, and this must be taken into account when evaluating their phonological development.
Table 2. Numbers of typically developing Mandarin-speaking 4-year-olds showing one or more mismatches by category.
Further to Table 2, there are a few children showing tone or vowel mismatches, even at age 4.
Acoustic analysis of the tone trajectories for Shanghainese Mandarin shows a smaller pitch range for the tones in comparison with the Beijing standard (Lai et al., 2011). Shanghainese has less extreme pitch changes in tones than Mandarin. The children's Mandarin may be Shanghainese-influenced, which may lead to mistranscription of tones, if transcription is based on standard Mandarin.
Additionally, the Shanghainese adult vowel space is smaller than that of adult Beijing Mandarin; the children's vowel space is smaller yet, and most likely is influenced by Shanghainese in this regard.
The point of this discussion is to stress the importance of always having normative data from adults of the dialect area, especially of the ages, genders, and occupations that tend to have close contact with preschool children. In this particular case, Mandarin may be a second language for many adults, who are likely to speak with a regional variant.
Word-structure segment interactions
Another source of variability in within-language data is the interaction between word structure and features. In data collected for Canadian (Manitoba) French, there were clear interactions between syllable stress and segmental production. In disyllabic words, /l/ and fricatives were significantly more accurate in stressed than unstressed syllables, as were nasal vowels. In multisyllabic words, all segments were more accurate in stressed than unstressed syllables (Bérubé et al., 2012). Thus, data
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analysis must necessarily evaluate variability in terms of syllable stress, word length, and syllable position.
Between-language diversity: Fricatives in German, English and Icelandic
Moving from within-language analysis to between-language analysis brings a whole new set of challenges in addition to the ones identified above. Assuming that all the transcription conventions are in place and that the data are reliable in terms of the transcription and of the identification of the adult target variant, the first thing to consider is whether the languages are similar enough to be compared (for the particular characteristics being focused on) and whether the samples are sufficiently matched to allow for comparison.
The first comparison in our crosslinguistic study was of German and English, two closely related languages (West Germanic) from the same family (Indo-European). A collaboration with Angela Ullrich in 2006 led to the launching of the whole crosslinguistic project. In comparing the data from German-speaking TD and PPD children (Ullrich, 2004) with English-speaking children's data, differences were noted suggesting that the language inventory and frequency of phonemes were relevant both in the timeline for mastery of phonemes and in the types of mismatch patterns that occur.
Because the German data for this crosslinguistic study were gathered in Cologne over a 2-year period, sufficient subjects were found to match the composition of the English sample relative to proportion of 3-, 4- and 5-year-olds, of gender and, to a certain extent, of the severity of PPD (English mean WWM = 12%, German mean WWM = 19%). Thus, comparisons between the whole German and English sample of children with PPD (30 children each) are considered valid (Bernhardt, Romonath,
& Stemberger, 2014). In contrast, for the Icelandic-English comparison, because the population of Iceland is so much smaller than that of Canada, it was impossible to match the two samples for WWM. It was necessary to find a matched subset of subjects, resulting in a sample of thirteen 3-year- olds and ten 4-year-olds from each language (Bernhardt et al., 2015). The following analysis highlights some commonalities between these two studies, providing additional information relative to fricative production in these three Germanic languages, as an example of similar challenges and diverse solutions.
The original motivation for examining fricatives was the observation that, in terms of segmental development, preschoolers with PPD often show a fairly high match proportion for stops, nasals and glides, but lower match proportions for and later mastery of fricatives. Thus, the fricatives, with their more complex articulatory characteristics, provide sufficient data for comparison across languages, especially in terms of mismatch types. However, the three languages do not have the same fricative inventories, and we needed to consider what could be compared (and what could not). The solution was to pick fricatives common to the languages being compared, matched for position in the word, and only in stress-initial words (avoiding any effects of word prominence, as noted in the previous section, and taking into account that all words in Icelandic are stress-initial). Here we focus only on word-initial position, because all three languages showed an accuracy level of about 38% for fricatives in that position.
Based on complexity and universal patterns of development, certain similarities among languages were predicted: (1) manner would be most affected, with stops as common substitutions across the languages; (2) /f/ would show the highest match levels (due to clearly observable visual cues); (3) grooving for sibilants would show the lowest match levels (with ungrooved substitutions), and the relatively infrequent interdental /θ/ would be less advanced; (4) voiceless fricatives would have higher match levels than voiced fricatives (for German and English, which have voiced fricatives, but not for Icelandic, which has approximants rather than voiced fricatives).
There were also a number of differences predicted for the different languages: (1) German voiced fricatives and / / would show higher match levels word-initially than the English ones, due to their higher frequency in German; (2) for mismatch patterns, more palatal substitutions were expected in